Takuya Ishikawa, Presenter: Nothing to Disclose

Haruhiko Machida MD, Abstract Co-Author: Nothing to Disclose

He Qing Wang MSc, Abstract Co-Author: Nothing to Disclose

Etsuko Tate, Abstract Co-Author: Nothing to Disclose

Yun Shen PhD, Abstract Co-Author: Employee, General Electric Company Researcher, General Electric Company

Eiko Ueno MD, Abstract Co-Author: Nothing to Disclose

Rika Fukui, Abstract Co-Author: Nothing to Disclose

Isao Tanaka, Abstract Co-Author: Nothing to Disclose

To investigate the optimal energy level of monochromatic images (MIs) for CT angiography (CTA) of mesenteric vasculature by single-source dual-energy CT (ssDECT) with fast kVp switching.

In 38 consecutive patients (20 men, 18 women; mean age, 64 ± 15 years; mean body mass index, 22.8 ± 3.1 kg/m2) undergoing CTA during the arterial phase by ssDECT (tube voltage: 80 and 140 kVp, switched during a single projection in as little as 0.25 msec; helical pitch: 1.375; collimation: 64 × 0.625 mm; noise index: 10 HU for 5-mm reconstruction; contrast medium dose: 600 mg I/kg; injection time: 30 sec), we measured averaged CT value of the abdominal aorta and its proximal branches (CT1) and the psoas muscles (CT2), standard deviation of CT value in the psoas muscles as objective noise (SD), and signal-to-noise ratio (SNR) as CT1 / SD and contrast-to-noise ratio (CNR) as (CT1 – CT2) / SD between the arteries and muscles on MIs at 40-90 keV. Two radiologists independently graded from one (poor) to five (excellent) the delineation of distal branches of the superior mesenteric artery, artifacts, and overall noise on maximal intensity projection CTA at 40, 55, 60, 70, and 85 keV. We compared those results among different energy levels using Tukey-Kramer test. We quantified inter-reader agreement regarding the subjective results using Cohen’s κ-statistics.

The CT value (CT1) steadily increased to 40 keV (1034.9 ± 264.5 HU); objective noise (SD) showed a trough at 71 keV (13.8 ± 2.1 HU) and increased to 40 keV (38.0 ± 6.0 HU); SNR was highest at 40 (27.7 ± 8.0) and 65 keV (27.2 ± 8.2) and CNR, at 40 (25.2 ± 8.2) and 61 keV (23.1 ± 8.1). The averaged subjective branch delineation was significantly higher at 40 (4.7 ± 0.6) than 60-85 keV (2.6 ± 0.8-4.3 ± 0.7); artifacts and noise improved significantly from 40 (3.8 ± 0.5; 3.6 ± 0.5, respectively) to 55 (4.4 ± 0.6; 4.6 ± 0.5) to 60-85 keV (4.9 ± 0.3; 4.9 ± 0.3-5.0 ± 0.2). The inter-reader agreement was substantial to excellent (kappa = 0.77-1.00).

The optimal energy level for CTA in the evaluation of mesenteric vasculature by ssDECT is 40 or approximately 60 keV.

In CTA of mesenteric vasculature by ssDECT, MIs at 40 keV should be used to depict small peripheral branches and diseases; otherwise, approximately 60 keV, as the standard of choice.

Ishikawa, T, Machida, H, Wang, H, Tate, E, Shen, Y, Ueno, E, Fukui, R, Tanaka, I, Optimal Energy Level of Monochromatic Imaging to Improve Vessel Delineation and Image Quality in Abdominal CT Angiography of Mesenteric Vasculature by Single-source Dual-energy CT with Fast kVp Switching.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14002239.html